Model Output Discussion

[snowmadchrisuk]

The 18z is going to pull in the Northerly like last night with -15 850's very close to Scotland at +150 (Thurs Next week) I think this is becoming the new trend .. Let's hope it doesn't get watered down this time .

[mcweather]

GFS 18Z 144 - 150HRS. I think thats what you call a retrogressing high

[Cloud 10]

ukmo144

gfs18z 144

Good agreement between these two at +144 for a potential northerly shot.

[cyclonic happiness]

The 18z has a good medium term and maybe a sign of things to come with one after the other northerly topplers, that's something we haven't seen for a while.

Too different all in all from all it's other runs to be too bothered about FI, the retrogressing high is looking increasingly interesting

[bluearmy]

the northern arm remains too strong on gfs for any real heights to build over greenland within the high res. liking the WAA up the west side of greenland on the T120 FAX. if the arctic pattern can do us a favour in a few days time, it could be game on.

[Eugene]

Cold anticyclonic spell or brief easterly likely before retrogression to greenland or out in the mid atlantic before HP building again, not a bad outlook at all after an excellent winter so far, people saying write off the atlantic at your peril, well all us cold weeather fans have to say is where has it been since early Dec apart from the odd day or two, all evidence points towards HP being the controlling factor with maybe the odd unsettled day here and there

Nice fax.

http://www.meteociel.fr/ukmo/fax/fax120s.gif

[nick sussex]

the northern arm remains too strong on gfs for any real heights to build over greenland within the high res. liking the WAA up the west side of greenland on the T120 FAX. if the arctic pattern can do us a favour in a few days time, it could be game on.

Well given the latest EPO forecast an amplified upstream pattern looks a certainty so its just how much thats in question.

http://www.esrl.noaa.gov/psd/forecasts/teleconn/images/compare.we.png

[mcweather]

the northern arm remains too strong on gfs for any real heights to build over greenland within the high res. liking the WAA up the west side of greenland on the T120 FAX. if the arctic pattern can do us a favour in a few days time, it could be game on.

Same here Blue army A good dose of WAA up the west coast of Greenland and as Nick suggests, an amplified jet pattern

then it could all get very interesting again as we head into february

[nick sussex]

Sorry to ask, but what is that showing? Thanks

Yes its the East Pacific Oscillation, heres a good explanation from NOAA. The current forecast is quite negative which is a good sign for western Europe.

The Eastern Pacific Oscillation (EPO) is the upper wind flow over the Eastern Pacific influenced by the ocean. When in a positive phase, the EPO generally is reflected by dominant stronger zonal flow and/or troughing along the West Coast of the U.S. This combination, in turn, tends to funnel milder Pacific air well inland into the country and thus, limits arctic outbreaks by holding them at bay up in Canada. When the EPO is dominated by a negative phase (as with the NAO), more ridging develops along the West Coast as higher pressure extends from the Gulf of Alaska south along the West Coast of Canada (opposite of the positive phase). This, in turn, encourages a northwesterly flow from Canada into the middle and eastern sections of the US and thus, the delivery of polar or arctic air.

Basically the ridge in the west USA and troughing over the east are more likely to lead to high pressure in the Atlantic, and then its down to the orientation of the trough as to how much WAA( warm air advection) you get going north into the Arctic. This then helps the development of high pressure to the east of the trough. So with the expected set up we want to see a deep east USA trough digging well south and orientated north/south this will drive warm air by way of southerlies on the eastern flank of the troughing into the Arctic with the aid of WAA this builds pressure near Greenland, downstream in Europe the cold air gets displaced and has to head south, however you need the right amplification so that the cold air heads south and not se otherwise the core of the cold heads into mainland Europe.

Edited January 21, 2010 by nick sussex

[BLAST FROM THE PAST]

Models seem to be catching onto the evolution quite quickly now. Details to change of course but the general idea is looking good and right. I believe that we are heading into a cold to very cold Feb, the jetstream will push south and any FI outlook of strong northern arm will disappear. This projection of retrograde and High pressure in Atlantic then heading north...looks familiar doesn't it?

Interesting to see The arctic is colder than average at the moment and are we looking at a SSW due to the very current activity [flares] from the sun?

BFTP

Edited January 21, 2010 by BLAST FROM THE PAST

[LomondSnowstorm]

Models seem to be catching onto the evolution quite quickly now. Details to change of course but the general idea is looking good and right. I believe that we are heading into a cold to very cold Feb, the jetstream will push south and any FI outlook of strong northern arm will disappear.

BFTP

Looking more like it BFTP. Your forecast so far for this winter has been pretty good, and the models seem to be moving more towards the PV dropping southwards into Scandinavia, bringing a northerly flow for late next week. FI will continue to throw up different scenarios after this point, but the signs are looking better now for some kind of height rise to our northwest. http://www.wetterzentrale.de/pics/Rtavn1561.png http://www.wetterzentrale.de/pics/Recm1921.gif http://www.wetterzentrale.de/pics/Rukm1441.gif The UKMO tonight was particularly good IMO, with heights rising more quickly over Greenland.

LS

[TEITS]

Unfortunately I haven't had chance to view the models until now.

For starters the Fax charts are excellent with the potential for snow showers especially in E areas. Beyond and I hate to say this but I can't see anything notable coming from the N,ly. Again using abit of instinct but I wouldn't be surprised if tomorrows ECM/UKMO/GFS have the main thrust of cold moving SE into Europe. At the moment I feel the N,ly flow will be coming over the top of the Atlantic HP rather than directly from the Arctic.

Lets hope tomorrows 0Zs prove me wrong.

Remember the further NW the Atlantic HP can be the colder and more prolonged the N,ly could be. If this fails and is centred just W of the UK not only will the N,ly be less cold but the HP is likely to topple eventually cutting off the N,ly flow. Also remember that there are many different types of N,lys. Just because the flow is from the N doesn't always mean it will be especially cold. Look out for the source of the N,ly rather than looking at the flow over the UK.

[PB22]

The stand off between the models continues this morning!

The 00z GFS is still very much against any easterly flow early next week, with this chart about as close as it gets:

http://www.wzkarten.de/pics/Rtavn781.html

http://www.wzkarten.de/pics/Rtavn782.html

This is the GEFS mean chart for T+96:

http://91.121.94.83/modeles/gens/run/gens-21-1-96.png?0

Doesn't look like many of the ensemble members are going for it either!

Meanwhile, the 00z UKMO is a pretty nice run:

http://www.wzkarten.de/pics/Rukm721.html

http://www.wzkarten.de/pics/Rukm961.html

http://www.wzkarten.de/pics/Rukm1201.html

http://www.wzkarten.de/pics/Rukm1441.html

The German model is closer to the UKMO output:

http://91.121.94.83/modeles/gme/run/gme-0-108.png

http://91.121.94.83/modeles/gme/run/gme-0-132.png

Judging by the Met Office forecasts, they are going with their own model with light snow showers currently being forecast for eastern areas on Monday, i.e. for eastern England:

Outlook for Sunday to Tuesday:Sunday will be mostly cloudy and dry, although some showers may arrive later. Monday and Tuesday will be cold, with mainly light snow showers, and a brisk easterly wind.

Updated: 0335 on Fri 22 Jan 2010

http://www.metoffice.com/weather/uk/ee/ee_forecast_weather.html

[Frosty.]

I think the Easterly is favourite to return during next week with some snow showers in the south & east and widespread sharp frosts, especially during the first half of the week and then there could be a Northerly by the end of next week although the ukmo 00z suggests the N'ly will be a near miss with not enough hp retrogression but the ecm 00z shows a direct hit N'ly with snow showers for the north and east later.

[West is Best]

Remarkable model divergence at short range overnight. The one consistent theme is an area of high pressure. It was this which gave me concern viz Bartlett, but all models are now progging the high about 400m north of that danger zone, at least in the short term. What makes the world of difference now though is the longitude. If UKMO verifies there's an easterly, but if GFS is closer to the mark we're perilously close to a pretty mild set up. I have to say that I favour the GFS. I expect to see the models continue to back away from the easterly as the Siberian high weakens and shunts further east, leaving most of the UK in a mild to very mild flow next week.

[cyclonic happiness]

Not convinced by the gfs output again this morning, it simply rolls over the HP as if it's not even a barrier and this is NOT a normal winter so why should it show that?

I think we'll get our easterly and then HP will retrogress to the mid atlantic and we may even end up with a similar situation to last time.

But , as others have said, we need the jet to behave, but it's been pretty good so far this winter and if it continues I may even buy it a thankyou present

[Frosty.]

Even if the GFS 00z is right, it would be cold until midweek in the south and east with early snow showers and a chance of N'ly topplers to follow as lows ride over the top of the atlantic high and push into scandinavia with some cold zoneality, especially in the north but I think the gfs has underestimated the siberian block and will flip back by the 6z.

Edited January 22, 2010 by Frosty039

[Polar Continental]

Well the GFS is still stubbornly sticking to its guns, producing only a gnat’s wind of an easterly, so at T90 only –5c 850’s scrape the east coast.

The ECM is better, getting the colder air much further east, before high pressure sinks over the country around T96.

The UKMO and GEM are by far the coldest with fresh easterly winds getting established from southern Scotland southward. Even snow showers in the south east at T96.

So the saga continues this morning.

[Snowyowl9]

I`ve never seen anything like this before GFS/ECM with a slack W/SW-ly under HP.

http://91.121.93.17/pics/Rtavn1201.png

http://www.wzkarten.de/pics/Recm1201.gif

Then we have UKMO this first model I looked at this morning followed by GEM with a very cold easterly and snow showers.

http://www.wzkarten.de/pics/Rukm1201.gif

http://www.wzkarten.de/pics/Rgem1441.gif

Both has been more persistant showing an easterly,the other 2 have been all over the place with next week.

[Severe Siberian icy blast]

Remarkable model divergence at short range overnight. The one consistent theme is an area of high pressure. It was this which gave me concern viz Bartlett, but all models are now progging the high about 400m north of that danger zone, at least in the short term. What makes the world of difference now though is the longitude. If UKMO verifies there's an easterly, but if GFS is closer to the mark we're perilously close to a pretty mild set up. I have to say that I favour the GFS. I expect to see the models continue to back away from the easterly as the Siberian high weakens and shunts further east, leaving most of the UK in a mild to very mild flow next week.

Disagree strongly,

The gfs is the only model that has the high sat over us , the ecm and ukmo has very cold outlooks , albeit slightly different evolutions , but both go for a potent enough easterly , the gfs has been good at picking up this trend first , as it did the last time , but like last time its backed away from the idea , but it will come bk to it with in the next 24hrs you'l see .

Also the gfs isnt a mild outlook like you'v suggested , it will be cold and frosty with the deep cold to our east paying us a visit from time to time , but this will change shortly i feel like i said .

[Nick F]

The stand off between the models continues this morning!

Judging by the Met Office forecasts, they are going with their own model with light snow showers currently being forecast for eastern areas on Monday, i.e. for eastern England:

http://www.metoffice.com/weather/uk/ee/ee_forecast_weather.html

UKMet t+72 fax issued earlier this morning for 00z Monday seems to back the UKMO global model output and is not too different from ECM either:

You'd have to back the Euros, but there's still time for the the Euros to back towards the GFS. IMO all stems with how quickly the jet returning south over the UK later this weekend and early next week moves east and this affects the track of that low dropping down the east coast, GFS is quite progressive in this respect. BBC forecasts seem confident this morning with respect to snow showers early next week.

Longer term, 00z GFS looks rather bland (as it does in the shorter term!) - a look at the 8-10 day mean H500 comparisons show that ECM amplifies the mid-Altantic ridge north more than GFS - GFS has lower heights over Greenland and the alignement of the trough over eastern N America is more positively tilted, which keeps the upper flow 'flatter' across the mid-Atlantic ad thus less amplification, so we see northerly unlikely from GFS:

[TEITS]

So the saga continues this morning.

Saga is exactly the right word this morning mate.

Obviously the UKMO is the best output this morning wrt to the E,ly. However the best model run this morning is the GEM which goes from a E,ly to a N,ly and then a NE,ly which is actually supported by the ECM at this timeframe.

If you were going to base your outlook on model consistency then it would probably be the UKMO/GEM with the GFS definitely in last place. However unfortunately there is little point in looking beyond the E,ly until this is finally sorted. Im afraid the old chestnut of following the fax charts is best at the moment.

Speaking of which a lovely fax chart this morning with snow spreading SW across some parts of the UK.

http://www.wetterzentrale.de/pics/brack2.gif

Followed by snow showers in E areas.

http://www.wetterzentrale.de/pics/brack2a.gif

[MR EXTREMES]

its amazing that talk of a slack easterly wont be that cold after all europe is not warm i agree stronger the colder but anything from the east is going to be cold even the southeast.

[Eugene]

Being a bit polite about GFS 00Z aren't you nick, it looks terrible.

T+84 hrs fax looks almost identical to last nights T+96 hrs though and different to GFS 00Z T+72 hrs so you have to say as all other runs are very good that GFS is just having one of its usual wobbles before the severe cold GFS runs appear

http://www.wetterzentrale.de/pics/brack2a.gif

[cooling climate]

The ECM and the GFS seem to me to be very similar for the early to middle part of next week

this does not mean to say they are right.

The UKMO produces a much better easterly and the difference are all down to an area of low

pressure running southwest to northeast up over Iceland and the eastern side of Greenland.

The UKMO has this much further west which allows the high to the east to ridge further north

west thus keeping the UK in a east to southeasterly airflow.

The GFS does not want to know about the northerly at the end of next week into the weekend

but I have a strong suspicion that this will come on board in future runs as to will the UKMO.

Edited January 22, 2010 by cooling climate